The Common Law

by Oliver Wendell Holmes

Whether this strict rule is based on the common grounds of liability, or upon some special consideration of past or present policy, policy has set some limits to it, as was mentioned in the foregoing Lecture.

Another case of conduct which is at the risk of the party without further knowledge than it necessarily imports, is the keeping of a tiger or bear, or other animal of a species commonly known to be ferocious. If such an animal escapes and does damage, the owner is liable simply on proof that he kept it. In this instance the comparative remoteness of the moment of choice in the line of causation from the effect complained of, will be particularly noticed. Ordinary cases of liability arise out of a choice which was the proximate cause of the harm upon which the action is founded. But here there is usually no question of negligence in guarding the beast. It is enough in most, if not in all cases, that the owner has chosen to keep it. Experience has shown that tigers and bears are alert to find means of escape, and that, if they escape, they are very certain to do harm of a serious nature. The possibility of a great danger has the same effect as the probability of a less one, and the law throws the risk of [155] the venture on the person who introduces the peril into the community.

This remoteness of the opportunity of choice goes far to show that this risk is thrown upon the owner for other reasons than the ordinary one of imprudent conduct. It has been suggested that the liability stood upon remote inadvertence. /1/ But the law does not forbid a man to keep a menagerie, or deem it in any way blameworthy. It has applied nearly as strict a rule to dealings which are even more clearly beneficial to the community than a show of wild beasts.

This seems to be one of those cases where the ground of liability is to be sought in policy coupled with tradition, rather than in any form of blameworthiness, or the existence of such a chance to avoid doing the harm as a man is usually allowed. But the fact that remote inadvertence has been suggested for an explanation illustrates what has been said about the difficulty of deciding whether a given rule is founded on special grounds, or has been worked out within the sphere of negligence, when once a special rule has been laid down.

It is further to be noticed that there is no question of the defendant's knowledge of the nature of tigers, although without that knowledge he cannot be said to have intelligently chosen to subject the community to danger. Here again even in the domain of knowledge the law applies its principle of averages. The fact that tigers and bears are dangerous is so generally known, that a man who keeps them is presumed to know their peculiarities. In other words, he does actually know that he has an animal with certain teeth, claws, and so forth, and he must find out the [156] rest of what an average member of the community would know, at his peril.

What is true as to damages in general done by ferocious wild beasts is true as to a particular class of damages done by domestic cattle, namely, trespasses upon another's land. This has been dealt with in former Lectures, and it is therefore needless to do more than to recall it here, and to call attention to the distinction based on experience and policy between damage which is and that which is not of a kind to be expected. Cattle generally stray and damage cultivated land when they get upon it. They only exceptionally hurt human beings.

I need not recur to the possible historical connection of either of these last forms of liability with the noxoe deditio, because, whether that origin is made out or not, the policy of the rule has been accepted as sound, and carried further in England within the last few years by the doctrine that a man who brings upon his land and keeps there anything likely to do mischief if it escape, must keep it in at his peril. /1/ The strictness of this principle will vary in different jurisdictions, as the balance varies between the advantages to the public and the dangers to individuals from the conduct in question. Danger of harm to others is not the only thing to be considered, as has been said already. The law allows some harms to be intentionally inflicted, and a fortiori some risks to be intentionally run. In some Western States a man is not required to keep his cattle fenced in. Some courts have refused to follow Rylands v. Fletcher. /2/ On the other hand, the principle has been applied to artificial [157] reservoirs of water, to cesspools, to accumulations of snow and ice upon a building by reason of the form of its roof, and to party walls. /1/

In these cases, as in that of ferocious animals, it is no excuse that the defendant did not know, and could not have found out, the weak point from which the dangerous object escaped. The period of choice was further back, and, although he was not to blame, he was bound at his peril to know that the object was a continual threat to his neighbors, and that is enough to throw the risk of the business on him.

I now pass to cases one degree more complex than those so far considered. In these there must be another concomitant circumstance known to the party in addition to those of which the knowledge is necessarily or practically proved by his conduct. The cases which naturally suggest themselves again concern animals. Experience as interpreted by the English law has shown that dogs, rams, and bulls are in general of a tame and mild nature, and that, if any one of them does by chance exhibit a tendency to bite, butt, or gore, it is an exceptional phenomenon. Hence it is not the law that a man keeps dogs, rams, bulls, and other like tame animals at his peril as to the personal damages which they may inflict, unless he knows or has notice that the particular animal kept by him has the abnormal tendency which they do sometimes show. The law has, however, been brought a little nearer to actual experience by statute in many jurisdictions.

Now let us go one step farther still. A man keeps an unbroken and unruly horse, knowing it to be so. That is not enough to throw the risk of its behavior on him. The [158] tendency of the known wildness is not dangerous generally, but only under particular circumstances. Add to keeping, the attempt to break the horse; still no danger to the public is disclosed. But if the place where the owner tries to break it is a crowded thoroughfare, the owner knows an additional circumstance which, according to common experience, makes this conduct dangerous, and therefore must take the risk of what harm may be done. /1/ On the other hand, if a man who was a good rider bought a horse with no appearance of vice and mounted it to ride home, there would be no such apparent danger as to make him answerable if the horse became unruly and did damage. /2/ Experience has measured the probabilities and draws the line between the two cases.